Electropolymerisation of catalytically active PEDOT from an ionic liquid on a flexible carbon cloth using a sandwich cell configuration

We report the electropolymerization of poly(3,4-ethylenedioxythiopene) (PEDOT) from an ionic liquid, butyl-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (C4mpyrTFSI) onto flexible carbon cloth electrodes. A continuous, homogeneous and well adhered coating of the individual cloth fibres is achieved by employing a sandwich cell arrangement where the carbon cloth which is soaked with electrolyte is placed between two indium tin oxide electrodes isolated from each other by a battery separator. The resultant PEDOT modified carbon cloth electrode demonstrates excellent activity for the oxygen reduction reaction which is due to the doping level, conductivity and morphology of the PEDOT layer and is also tolerant to the presence of methanol in the electrolyte. This simple approach therefore offers a route to fabricate flexible polymer electrodes that could be used in various electronic applications

A six chemical species CFD model of alumina reduction in a Hall-Héroult cell

The industrial process for producing primary aluminium metal is the reduction of powdered alumina in a Hall-Héroult reduction cell. These cells operate at temperatures above 940 °C with a highly corrosive electrolyte making physical measurement of the process difficult or nearly impossible. Computational models of the electro-magnetic fields and heat transfer are widely used in industry to design cells. Only recently (Feng et al., 2010b, Witt et al., 2012) have detailed computational models of the molten liquid-gas bath become available. Alumina distribution within the cells is important for cell efficiency and preventing anode effects. Using the bath flow information and an assumption of uniform reduction, a single scalar transport equation has been used to track the time variation of alumina within cells (Feng et al., 2011). In this work the previous single species model is extended to include six chemical species and four chemical reactions. The reaction pathway developed for the model is that solid alumina particles are fed to the bath surface, where they mix and submerge into the liquid bath, and then undergo dissolution from solid particles to the liquid species Na2Al2O2F4. Within the bath Na2Al2O2F4 converts to Na2Al2OF6, which is involved in an oxidation reaction with carbon to produce carbon dioxide and AlF3 at the anode surface. At the metal pad a cathodic reaction occurs with AlF3 converting to aluminium metal. Species solubility rates are based on the work of Solheim et al. (1995). A CFD model of a single anode in a bubbly cryolite bath was built based on a corner anode from an industrial cell. Steady state bath flows were calculated and used to transport the six chemical species in the new bath chemistry model. Results were obtained for 20,000 seconds of real time for species distributions in the anode to cathode distance (ACD), change in mass of species in the bath with time, rates for the four reactions at locations in the bath and change in the species mass fraction with time at various locations during a feeding cycle

A six chemical species CFD model of alumina reduction in a Hall-Héroult cell

The industrial process for producing primary aluminium metal is the reduction of powdered alumina in a Hall-Héroult reduction cell. These cells operate at temperatures above 940 °C with a highly corrosive electrolyte making physical measurement of the process difficult or nearly impossible. Computational models of the electro-magnetic fields and heat transfer are widely used in industry to design cells. Only recently (Feng et al., 2010b, Witt et al., 2012) have detailed computational models of the molten liquid-gas bath become available. Alumina distribution within the cells is important for cell efficiency and preventing anode effects. Using the bath flow information and an assumption of uniform reduction, a single scalar transport equation has been used to track the time variation of alumina within cells (Feng et al., 2011). In this work the previous single species model is extended to include six chemical species and four chemical reactions. The reaction pathway developed for the model is that solid alumina particles are fed to the bath surface, where they mix and submerge into the liquid bath, and then undergo dissolution from solid particles to the liquid species Na2Al2O2F4. Within the bath Na2Al2O2F4 converts to Na2Al2OF6, which is involved in an oxidation reaction with carbon to produce carbon dioxide and AlF3 at the anode surface. At the metal pad a cathodic reaction occurs with AlF3 converting to aluminium metal. Species solubility rates are based on the work of Solheim et al. (1995). A CFD model of a single anode in a bubbly cryolite bath was built based on a corner anode from an industrial cell. Steady state bath flows were calculated and used to transport the six chemical species in the new bath chemistry model. Results were obtained for 20,000 seconds of real time for species distributions in the anode to cathode distance (ACD), change in mass of species in the bath with time, rates for the four reactions at locations in the bath and change in the species mass fraction with time at various locations during a feeding cycle.ACKNOWLEDGMENTS. The present work was supported by the project “Gas and Alumina Distribution and Transport” (GADT), financed by the Research Council of Norway and Hydro Primary Metal Technology. Permission to publish the results is gratefully acknowledged. The authors wish to acknowledge the valuable discussions and advice provided by Asbjorn Solheim on the electro-chemical reactions, rates and processes in aluminium reductions cells.publishedVersio

Electrochemical Tailoring of Fibrous Polyaniline and Electroless Decoration with Gold and Platinum Nanoparticles

Presented in this work is a facile and quick electrochemical method for controlling the morphology of thick polyaniline (PANi) films, without the use of templates. By stepping the polymerization potential from high voltages to a lower (or series of lower) voltage(s), we successfully controlled the morphology of the polymer, and fibrous structures, unique to each potential step, were achieved. In addition, the resultant film was tested electrochemically for its viability as an electrode material for flexible batteries and supercapacitors. Furthermore, the PANi film was decorated with gold and platinum nanoparticles via an electroless deposition process for possible electrocatalytic applications, whereby the oxidation of hydrazine at the composite was investigated

Improving the rate capability of LiFePO4 electrode by controlling particle size distribution

In this study, the rate performance of a LiFePO4 (LFP) electrode has been enhanced by optimization of the particle size distribution of the LFP particles. Two LFP samples with different particle sizes (∼50 and ∼350 nm) are mixed with various ratios and the electrochemical performance has been evaluated. Reduction of the contact resistance and increase of the Li diffusion coefficient have been achieved. The electrode with a mixing ratio of 50:50 shows an improved initial capacity at C/10 and superior rate capability compared with the two pristine materials.</p

Nanoscale characteristics of practical LiFePO4 materials - Effects on electrical, magnetic and electrochemical properties

LiFePO4 (LFP) is one of the important commercial battery materials, as such, many efforts have been made to understand its electrical and ionic conductivities and electrochemical properties. In this study, we have investigated electrochemical, electrical and magnetic properties of carbon coated LFP down to cryogenic temperatures. The fact that the practical material really consists of a core-shell structure with a shell of delithiated material and carbon coating determines the measured properties, which are often mistakenly attributed to pure LFP core behaviour. An electronic resistivity drop (11 ± 0.5% based on the resistivity at room temperature), preceded by a gradual increase feature between 100 and 30 K, was observed when the temperature was below the Néel temperature at low applied currents, indicating a likely interaction between the magnetic configuration of the core LFP and electronic transport mechanisms. Metallic Fe3P was precipitated on the samples surfaces after annealing at high temperature in Argon. The existence of Fe3P was found to significantly improve the electronic conductivity but it took a toll on the electrochemical performance.</p